Art of radiosignaling



Oct. 31, 1933. L COHEN 1,932,397

ART OF RADIOSIGNALING Filed Dec. 11,' 1929 2 Sheets-Sheet 1 Get. 31, 1933. L. COHEN ART OF RADIOSIGNALING Filed Dec. 11, 1929 2 Sheets-Sheet 2 Patented Got. 31, 1933 PATENT OFFICE ART OF RADIOSIGNALING Louis Cohen, Washington, D. 0.

Application December 11, 1929 Serial No. 413,369

10 Claims. (01. 250-20) tion of interference caused by other signals of definite periodic character-as those, for instance, emitted by other transmitting stations. When interference, however, is caused by irregular disturbances, as those produced by static discharges in the atmosphere, or other electrical disturbances of an irregular character, the method of progressive tuning is no longer effective. It is a common experience in the use of broadcast receivers, that though provided with several stages of tuned radio frequency amplification, static disturbances when present in the atmosphere come through nevertheless, and at such times render reception difficult and frequently almost impossible. This applies to the reception of telegraph signals as well as speech or musical signals.

In this invention an entirely novel method is proposed by which a high degree of selectivity in the reception of signals is obtained, and which is equally eflicient in the elimination of irregular disturbances such as static discharges as well as disturbances caused by undesired signals from other transmitting stations. Static discharges are generally of an impulsive character, and when acting on an oscillatory circuit, the current produced in the circuit by such impulses consists of two components, one of which is of the same character and form as the impulse which produces the current in the circuit, and the other component is a damped oscillatory current, the frequency and damping of which are determined by the electrical constants of the circuit and independent of the shape or form of the impulse producing it. The impulsive component of the current is by far the more important one and more difficult to eliminate from a receiving circuit system, progressive tuning cannot do it. The impulsive components are transmitted from one circuit to another without any regard to the tuning of the circuits.

The method proposed in this invention provides for dividing the energy collected by the antenna between two circuit systems which are balanced against each other, and so designed as to balance out all interfering signals of Whatever character except the signals of a particular frequency which is desired to receive, and for which the system is in adjustment. The method and the principles of operation are best explained by reference to the accompanying drawings which form part of the specification:

Figure 1 illustrates diagrammatically an embodiment of the invention comprising two balancing circuits associated through two independent vacuum tube amplifiers with the antenna.

Figure 2 is a diagram showing a modification in which the two balancing circuits are associated with the antenna through a single vacuum tube amplifier. Figure 3 is a diagram showing a further modification which provides for the tuning of the antenna. I

Having particular reference to the accompanying drawings, in which like numbers designate similar parts throughout, in Fig. 1, antenna 1 is connected to the two grids of thevacuum tube amplifiers 2 and 3, the plate or output circuit of amplifier tube 2 comprising a coupling coil 4 by which the plate circuit is coupled to the oscillatory circuit 6, while the output circuit of tube 3 is coupled to the oscillatory circuit '7 by coil 4'. The two oscillatory circuits 6 and '7 are again coupled differentially to a common circuit 8 through couplings 9 and 10; the terminals of circuit 8 are connected to the grid G and filament F of the first tube of an amplifying system designated by the box 11. If no radio frequency amplification is desired, the terminals of circuit 8 may connect directly to the grid and filament of a detector tube. Again, interstages of the radio frequency amplifier 11 may be associated with a suitable tuning circuit to provide additional tuning if desired in the usual method in the practice of the art. The oscillatory circuits 6 and '7 are adjusted for the same oscillation frequency and to be in resonance for the frequency of the Signals desired to receive, that is Ls Ca=L7 C7 and also satisfy the relation 21r /LC A, r where f is the frequency of the signals desired to receive. The ratios, however, of L to C in the two circuits are different, that is, the ratio 5r s isseveral times greater than the ratio 51 .07 i This condition is obtained by using a larger inductance and smaller capacity in circuit 6, than those of circuit 7. It is also necessary for the successful operation of the system that the resistances of the two oscillatory circuits 6 and 7 should be substantially the same, and since the resistance of circuit 6 is apt to be higher because of the larger inductance in that circuit, it is to be compensated for by the introduction of an additional resistance 12 in circuit 7. Circuit 8 is coupled differentially to circuits 6 and 7 so that the elec tromotive forces induced in circuit 8 from 6 and 7 are oppositely directed. The mutual inductance however, of coupling 9 should be greater than the mutual inductance of coupling 10, and the two should be in the same ratio as L6 to L1 that is, if L6 is to be made three times greater than L7, for instance, then the mutual inductance between 13 and 14 should be also made three times greater than the mutual inductances between 15 and16. The matter of adjusting the mutual inductances in the proper ratios is accomplished by either varying the number of turns or the distance separation of the coils in well known manners.

The operation of the system is as follows: When 7 a signal is impressed on the antenna which is of a V frequency for which circuits 6 and 7 are in resonance, then the currents produced .by that signal in circuits 6 and 7 will be inversely proportioned to the resistances of the circuits, and since the resistances in the two circuits are the same, the

currents will have the same values. Since, however, the mutual inductance of transformer 9 is several times greater than that of transformer 10,

different magnitudes, there is a resultant voltage in that circuit to act on the grid of 11, and by amplification and detection produce a response in the indicating instrument. The matter of detecting and indicating means are well known in the art; the conventional methods may be used and do not form part of the invention. It is for this reason that the amplifying and detecting means are designated here simply by a box marked 11. It should be pointed out, however, that circuit 8 is practically an open circuit because of the small capacity between grid and filament forming part of that circuit, and, therefore, does not produce any electrical interaction between circuits 6 and 7. By this arrangement circuits 6 and 7 function entirely independently of each other. For interfering signals or frequencies different from the frequencies for which circuits 6 and 7 are in resonance, the response in the circuits are inversely proportioned to the reactances of the circuits, and since circuit 6 has a greater inductance and smaller capacity, its reactance is greater than that of circuit 7, and precisely in the ratio of L6 to L7. Hence, the current produced in circuit 6 by the signals is smaller than that produced in circuit 7 in the same ratio. Since, however, the mutual inductance between 13 and 1a is greater in the same proportion than the mutual inductance between 15 and 16, the E. M. F.s induced in circuit 8 by the currents from circuits 6 and 7 will be of the same magnitude but of opposite directions and, hence, neutralize each other,

balancing out each other completely from circuit 8 and producing no effect whatever on the grid of 11, rendering the system entirely free from interferences of such signals. This method is equally effective in balancing out interferences produced by irregular disturbances, such as static discharges and others. In the case of irregular disturbances, the impulses acting on the antenna also produce currents in circuits 6 and 7 of magnitudes in inverse ratio to the inductances in these circuits, hence, because of that, the E. M. Ffs induced in circuit 8 by the currents in the circuits 6 and 7 balance out eachother precisely in the same manner as described above in connection with the action of interfering signals of an oscillatory character of definite frequencies. The ad vantage of this method resides in its'eflectiveness for the elimination of all sorts of interferences, screening the receiver proper from any electrical disturbances of whatever character, and thus securing a degree of selectivity not obtainable by the usual methods now used in practice. In the circuit system of Fig. 1, an untuned antenna is shown connected to the grids of the two tube amplifiers 2 and 3. This is only one way of using the system. The antenna may be grounded at 17 as shown by the dotted line connecting 17 to ground 18. The antenna may be also grounded through an impedance and the signal voltage drop across that impedance applied to the grids of the 108 2 in which the two balancing oscillatory circuits i O5 are linked to the antenna through a single tube amplifier. The antenna 1 is grounded at 18 through the resistance 19. The voltage drop developed across the resistance 19 by any signal energy acting on the antenna is applied to the 1'10 grid and filament of the tube 20. The plate circuit 21 is coupled to two oscillatory balancing circuits 6 and 7 which are in turn coupled by transformers 25 and 26 to a common circuit 8.

The adjustments of circuits 6 and 7 and the conplings 9 and 10 are the same as described in connection with Fig. 1, and the operation of the system is also the same. For signals of a frequency for which the'circuits 6 and 7 are in resonance,

a voltage is produced in circuit 8 which is trans mitted to the grid and filament of 11, and through amplification and detection produces an effect in the indicating instrument, usually a telephone or loud speaker, in which the signals are audible.

For any interfering signals, the currents in circuits 6 and 7 induce electromotive forces of the same magnitudes but of opposite directions in circuit 8 in the manner described in connection with Fig. 1, balancing out completely the elfects of such interfering signals.

The modification shown in Fig. 3 differs only from that of Fig. 2 in thatthe antenna circuit itself is provided with tuning elements of inductance 22 and variable capacity 23; the rest of the circuit system is the same as that of Fig. 2.

In allthe arrangements shown in the figures, care must be taken to keep circuits 6 and 7 in such positions and distance apart as to prevent any direct electrical or magnetic action between them.

It is understood that many modifications may 1% be introduced embodying the principles of this invention without departing from the scope and character of this invention.

I claim:--

1. A system for the reception of radio signals 2.3.

for resonance to the frequency of the signals demeans for adjusting the couplings between the said'two tuned circuitsand the said third circuit.

2. A system for the selective reception of radio signals which comprises a means for intercepting desired and undesired signal'energ'y, t'wo oscilla- -tory circuits, and two tube amplifiers to couple "said circuits tosaid means; means for adjusting each of said tw'o oscillatory circuits'to resonance forthe frequency ofthe signals desired to receive; the ratio of inductance to capacity being differentin e'achof the said two oscillatory circuits; means for opposing the electrical effects produced in the said two oscillatory circuits by incoming signals in their action on a third common circuit; means for adjusting said last mentioned means to produce in said third common circuit a resultant effect for signals of the frequency for which the said two oscillatory circuits are in resonance adjustment, and to balance out the electrical effects of all other signals which may be transmitted from the energy intercepting means to the said common third circuit.

3. A system for the reception of radio signals comprising an antenna, two vacuum tube amplifiers, the signal energy collected by the said antenna being applied to the grids of the said two vacuum tube amplifiers, an independent oscillatory circuit coupled to the plate circuit of each of the said two vacuum tube amplifiers; each of said independent oscillatory circuits being adjusted to resonance for the frequency of signals desired to receive, the ratio of inductance to capacity in the said two oscillatory circuits being different; means for combining the voltages developed in the said two oscillatory circuits by incoming signals in their action on a third circuit in opposite directions, to produce in said third circuit a resultant electrical effect for the signals for which the said two oscillatory circuits are'in resonance adjustment, and to balance out the electrical effects resulting from all other signals.

4. In a system for the reception of radio signals comprising energy pick up means, two vacuum tube amplifiers, the signal energy collected by the said energy pickup means being applied to the grids of the said two vacuum tube amplifiers, an independent oscillatory circuit coupled to the plate circuit of each of the said two vacuum tube amplifiers; the circuit elements of oneof said oscillatory circuits being of diiferent magnitudes than the corresponding circuit elements of the other of said oscillatory circuits; each of said oscillatory circuits being adjusted to resonance for the frequency of the signals desired to receive; means for opposing the electrical effects induced from the said two oscillatory circuits in a third circuit which is in electrical association with the said two oscillatory circuits to'produce in the said third circuit a resultant electrical effect for the signals of the frequency for which the said two oscillatory circuits are in resonance adjustment, and to balance out all electrical effects produced by other signals. 7

5. A system for the reception of radio signals comprising an antenna, two vacuum tube amplifiers, the signal energy collected by the said antenna being applied to the grids of the said two vacuum tube amplifiers, an independent oscillatory circuit coupled to the plate circuit of each of said two 'vacuum tube amplifiers; the circuit elements of one of said oscillatory circuits being of different magnitudes than the corresponding circuit elements of the other of said oscillatory cir'cuitspmeans' for adjusting each of said oscillatory circuits to resonance for the frequency of signals desired to receive; means for coupling oppositely the saidtwo oscillatory circuits to a common third circuit, inducing thereby, by the signal energy transmitted to the said two oscillatory circuits; electr'o-motive forces of opposite directions in the said third circuit; means for ad.-

justing the said couplings between the said two oscillatory circuits and the said third common circuit in relation to the relative magnitudes of the circuit elements of the said .two oscillatory circuits toproduce a resultant electromotive force in the said third circuit for signals for which the said two oscillatory circuits are in resonance adjustment, and to balance out electro-motive forces induced in said third common circuit from signals of other frequencies.

6. In a system for the reception of radio signals comprising energy pick up means, two oscillatory circuits adjusted to the same resonance frequency but the circuit elements of one of the said circuits being of different magnitudes than the cor-- responding elements of the other of the said tuned circuits; means for opposing the electrical effects produced in said circuits in their actions on a common circuit; and vacuum tube means for coupling said two oscillatory circuits to the said energy pick up means.

'7. In a system for the reception of radio signals comprising energy pickup means, two oscillatory circuits adjusted to the same resonance frequency but the circuit elements of one of the said circuits being of different magnitudes than the corresponding elements of the other of the said tuned circuits, means for opposing the electrical effects produced in said circuits; vacuum tube means for coupling said two circuits to said energy pick up means, said vacuum tube means comprising two three-electrode vacuum tubes, the grids of each tube being connected to said energy pick up means, and the plate circuit of each tube being coupled to one of the oscillatory circuits.

8. A system for the reception of radio signals comprising energy pick up means, two vacuum tube amplifiers associated with the said energy pickup means, a tuned circuit coupled to each of the plate circuits of said tube amplifiers, each of said tuned circuits being adjusted for resonance to the frequency of the signals desired to receive, the circuit elements of each of the said two tuned circuits being of different magnitudes, means for opposing the output of said two tuned circuits in their action on a common circuit to produce a resultant electro-motive force in the said common circuit by the signals of the frequency desired to receive while balancing out interfering signals;

9. In a system for the reception of radio signals, comprising an antenna circuit, two vacuum tube amplifiers, two oscillatory circuits and a common circuit; the voltage developed on the antenna by incoming signals being impressed on the grids of the said vacuum tube amplifiers; one of the said two oscillatory circuits being coupled to the plate circuit of one of said vacuum tubeamplifiers and the other oscillatory circuit being coupled to the plate circuit of the other vacuum tube amplifier; the said two oscillatory circuits being adjustedjto resonance for the frequency of the signals desired to receive, but the induci.

tube amplifier, two oscillatory circuits and a common circuit; the voltage developed in said energy pickup means by incoming signals being impressed on the grid of the said vacuum tube amplifier; means for coupling the said two oscillatory circuits to the plate circuit of the 7 said vacuum tube amplifier; each of the said two oscillatory circuits being adjusted for resonance to the frequency of the signals desired to receive; the ratio of inductance to capacity of each of the said two oscillatory circuits being of different magnitudes; means for coupling the said two oscillatory circuits differentially to the said common circuit; the magnitudes of the said couplings being adjusted to balance out from the said common third circuit theeifects resulting from interfering signals while producing in it a resultant electromotive force for the signals of the frequency desired to receive.

LOUIS COHEN. 

